The combination of a combustion engine such as an internal combustion engine and a generator to produce electrical power has been known for many years. Relatively more recently, however, engine-driven generators have been used in electrically powered mobile machines to provide electrical power for propulsion and operation of other machine systems. In such strategies, rather than requiring relatively rapid ramp-up and down of engine output to accommodate changes in power demand, relatively more stable, smooth operation and transition across an engine power output range may be achieved. In other words, by powering some or all of the machine systems with electrical power provided by an on-board engine and generator system, combustion characteristics and overall engine operation can be more predictable and changes less rapid. This allows wide and rapid swings in engine speed and load associated with changes in power demand on the system to be avoided. Where engine operation is more predictable, and changes in engine output more gradual, superior control over emissions and other factors such as fuel efficiency has been demonstrated as compared to traditional designs wherein an engine directly powered the machine propulsion system, hydraulics, etc.
While the aforementioned developments have provided improvements to certain machines, particularly in environments where jurisdictional regulations set forth relatively high standards for emissions and efficiency, a variety of new challenges have arisen. For instance, in certain machines, particularly heavy-duty machines such as construction machines, mining machines, etc., a relatively large generator output is often necessary to provide sufficient power for running the machine. Most generators utilize components whose size is directly correlated with available generator output. Hence, electrical power systems for such machines often employ a generator with a relatively large rotor and other components, necessarily increasing the generator's internal inertia. The high generator inertia can give rise to mounting and other hardware-related challenges due to vibrations and inertia reflection between the engine and generator.
In many machine systems where an engine directly drives a generator vibrations and inertia associated with system operation can be transmitted between the engine and the generator. This can be particularly problematic where the generator inertia is fairly close to that of the engine. In some instances, resonance vibrations in the system can result in significant torque spikes within the system, at minimum wasting energy and roughening operation, and in certain instances even damaging components. While some system designs are sufficiently robust to withstand torque spikes when accelerating or decelerating through a speed range where resonance vibrations tend to occur, these systems can have other drawbacks, such as higher weight and cost.
Challenges associated with operating high-inertia electrical power generation devices with an engine have been previously recognized. United States Patent Application Publication No. 2003/0155202 A1 to Taniguchi is directed to a system wherein an alternator is driven by an engine. The alternator and engine are coupled together via a driving belt through a one-way clutch that transmits engine torque to the alternator and intercepts torque transmission from the alternator to the engine by allowing oscillatory relative rotation. Other strategies, also noted by Taniguchi, rely upon the use of torsional springs or other means for introducing torsional compliance into such alternator-engine systems. None of these known strategies, however, are concerned with nor provide any suitable means for addressing the above mentioned resonance vibration problems.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.